This year I have been studying Yang Taijiquan deeply with Coach Chris Pei of United States Wushu Academy in Falls Church Virginia. Some of the classes have involved taking a theme from the 10 essences and apply it in Long form study. We are also to memorize the 10 Essences, it comes to make for a great story. Here is how I describe it. The first 5 essences are physical while the last are mental.
The second half begins the mental training once you are able to master the first 5.
6. Once you begin to understand the separation of weight you can begin to move and practice coordination of the upper and lower parts of the body with stepping.
7. Continuity of movement is achieved when you can separate the weight, coordinate the upper and lower body without interruption as a connected whole.
8. The quality of the continuity must be harmonized from the inside with a soft pliable internal energy (qi) and physical frame (external) is performed without too much hard and tense strength (Li).
9. The inside of the frame must be coordinated with the outside of the frame (balance/middle path).
10. Using the mind “shen” (Yi: will and intent) you will be able to achieve stillness in movement and movement in stillness when all 10 of these principles are harmonized in your Taijiquan practice.